I have a set of Ryobi tools that use 18V Li-ion batteries. I have two batteries and I have heard people say to leave the extra battery on the charger until the other runs out of juice. I've also heard and red that you are not supposed to do that. Also, I'm seeing a lot of confused info about Ni-cad and Li-ion.

Also, I bought a generic replacement battery for the Ryobi. What a complete waste. Fully charged it will run the tool for 1 second and then stop. Then again and again until you are worn out from pulling the trigger. Also the generic is much lighter than the Ryobi. Bought on Ebay for $30 and the Ryobi is $60. Guess you don't even get what you pay for.